a) Technical Field of the Invention
This invention relates to an isolation switch and particularly to an active isolation switch for power supply.
(b) Description of the Prior Art
Nowadays, multiple power supply modules are combined to form a structure of a redundant power system. Power supply modules are connected in parallel to form a common power bus. OR-ing circuit elements are necessary to be included between the power supply's output. This is to prevent a failure of one power supply module to cause a system failure, thus achieving the redundancy requirement.
However, the existing common ORing circuit has the following drawbacks: the comparator input offsets exist and these offsets will affect the FET through a breakpoint on the FET control; when the offset is positive, it will be caused that the output current is relatively small and thus the FET does not open, and it is generally necessary to make the turn-on threshold of the comparator be closer to negative voltage limit, but in this case, it is inevitable that when the bus voltage is higher than the module voltage, there is reverse current fed back to the module from the bus, and that when the reverse current does not reach a certain threshold, the FET cannot be turned off. Also, the comparator is required in the existing ORing circuit, so the cost of the circuit get higher.
Consequently, because of the technical defects described above, to provide the improver, the applicant, based on many years of research and experience in the relevant industry, has developed the present invention, which may effectively improve the defects described above.